LED lights for flies

LEDs produce intense beams of UV-A light that penetrate further into the surrounding environment and appears more attractive to certain insects - like house flies - than the light traditional phosphor lamps produce.

The house fly is attracted to UV-A as their eyes are sensitive to light at that wavelength.

Wavelengths of light which fall outside the visible light range are more attractive to house flies than those that fall within it.

Why are flies attracted to light?

A phenomenon known as phototaxis describes how insects respond to light.

Certain insects, such as cockroaches or earthworms, have negative phototaxis, meaning they are repelled by an exposure to light. Moths, flies and many other flying insects have positive phototaxis so are naturally attracted to it.

While there is no single scientific explanation for flies’ attraction to light, there are several theories for why this happens.

Light used for safety

For some insects, a bright light source may be seen as a safety signal. Light sources are generally positioned on higher ground, so instinctively heading towards light helps to keep insects away from hazards near the ground.

Light used for navigation

Another popular theory is that insects use light as a navigational aid.

An insect flying north, for example, is able to judge its direction by keeping a natural source of light, such as the sun or moon, on its right.

This method works well as long as the source of light remains both constant and at a distance.

If an insect encounters another light source, such as a round incandescent porch light, it becomes confused. This explains why a moth may continuously encircle a light -as it instinctively wants to keep the light on a certain side of its body to help it navigate its route.

Artificial vs. natural light

There is some debate in the scientific community over why a positively phototactic insect will continue to hover around an artificial light source even when natural light becomes available.

Some believe that the insect is not attracted to the light itself, but the darkness surrounding it.

Others suggest the insect’s eyes, which often contain multiple lenses, struggle to adjust from light to dark. This leaves the insect night-blind and vulnerable to predators, so the insect may find it safer to remain in the light rather than fly away.

Fly killer testing

Since 2008, Rentokil's Global Technical Centre has dedicated two purpose-built rooms to testing fly killers. Units are compared using a standard performance test called the half-life measure.

All of our fly killers have been subjected to the same rigorous testing ever since, including the new Lumnia fly killer range.

Rather than reading the percentage catch directly (blue), Graph 2 indicates how the half-life value (red) is a measure of flies caught in the fastest time.

The Rentokil test is based on releasing 100 house flies (Musca domestica) in a standard test room with the product/ unit installed, and counting the number of flies captured at regular intervals over a seven hour period.

This process is repeated at least six times to ensure a fair reflection of performance over time

The half-life measure represents the time taken to eliminate 50% of the flies released in the test chamber